Metallic soaps, their complex soaps and mixed soaps of Na—Al, or Li—Ca have generally been reported in the prior art as thickeners in the lubricating grease industry. Use of a mixed base soap is an upcoming trend. The use of mixed soaps provides added advantages in actual application areas because of the mixed characteristics of both the soaps.
Polishuk, in ‘Brief History Of Lubricating Greases’ describes different types of mixed base greases viz, Al—Ca, Al-complex-clay base, Ba—Al base, Al-complex-Na base, Ca—Al, Ca—Pb, Li—Ca. See also U.S. Pat. Nos: 2,379,245; 2,332,247; 2,209,500; and 3,595,789. Some of the mixed base greases prepared by many researchers did not obtain commercial appreciation; this may be due to incompatibility of the two soaps, an antagonistic effect of the two different soaps, or other reasons. Polishuk reported in U.S. Pat. No. 3,620,975 the preparation of an Al-complex-clay base grease for passenger car applications which consists of 2.1% stearic acid, 1.2% benzoic acid, 5% of a derivative of Al-alkoxide, 1% baragel clay, and additives. This grease was reported to perform better in wheel bearing application. Zimmer and Morway (U.S. Pat. No. 2,062,346) prepared a Ca—Al base grease by use of 12% Ca-soap, 10-15% Al-soap, 1% glycerine and mineral oil (300 SUS @ at 100° F.) and reported it to be improved in adhesive and water resistant properties. Morway and Ramsden (U.S. Pat. No. 3,223,633) reported Li—Ca greases for channeling applications which was of 4.1% LiOH, 15% hydrofol acid 51, 2% hydrated lime, 3.0% azelaic acid, and 3.0% acetic acid. This grease was reported to have an ASTM penetration of 245 and a drop point over 450° F. Over a period of time Li—Ca base greases have become more popular, probably because of their excellent water resistance characteristics and other commercial reasons.
It is found interesting to note that, a majority of soap or complex soap thickeners of commercial significance for formulating lubricating greases are metals derived from either alkali or alkaline earth metals. Metallic soap thickeners from transition metal elements, such as titanium, for formulating lubricating greases have been reported in U.S. Pat. No. 5,387,351 of the applicants herein. However, mixed thickener base greases of transition metals like titanium and other metallic soaps have not been reported at all in the literature. However, Applicants have expected that, if mixed soaps based on titanium as one of the components are formed, they may exhibit high performance properties.